The present invention relates to a disc driving apparatus equipped with an optical pickup for reproducing or reproducing/recording information on an optical disc; and, in particular, the invention relates to a disc driving apparatus which is suitable for as a so-called CD-ROM drive, a DVD-ROM drive, and a DVD-RAM drive, etc.
A laser light generation device and an optical disc read-out/write-in apparatus equipped therewith have been described in, for example, Japanese Patent Laying-Open No. Hei 10-283650 (1998) (conventional art 1). In such a device, a thermally conductive sheet is disposed between a first heat radiation member and a second heat radiation member, wherein the area of control is increased between the first heat radiation member and the second heat radiation member, compared to the case where both members are in contact with each other directly. Thereby, radiating heat, which is generated in a heat generating element, such as a semiconductor laser element, flows into the second heat radiation member effectively, so as to cool down the semiconductor laser element with high efficiency.
Also, an optical pickup was described in, for example, (conventional art 2). In such an optical pickup, by using a prism made of plastic therein, an optical pickup is provided that can detect an excellent signal without causing shifting of the optical axis within the plastic prism due to a change of temperature. In this regard, a spacer for purposes of heat insulation is placed between an optical system forming the optical pickup and a silicon substrate on which a laser diode, appearing as a heat generating element, is provided for emitting a laser light beam into the optical system, so as to form a layer of air having low thermal conductivity, thereby enabling radiation of heat from the laser diode into the silicon substrate.
However, in the above-described conventional arts 1 and 2, there is no disclosure concerning deterioration of the lifetime of parts or elements, erroneous operation, or a decrease in the reproducing/recording accuracy, accompanying a non-uniform local temperature distribution, due to thermal interference between adjacently disposed heat generating elements and/or heat generation of a heat-generating element. Therefore, there is a possibility that, in a case where plural numbers of heat-generating elements are disposed at neighboring locations relatively close to each other, due to the thermal interference between the heat-generating elements, elements having a small heat generation amount and/or elements of low heat-resistance or endurance are affected with the thermal influences provided by other heat-generating elements, erroneous operation, and/or a decrease in the reproducing/recording accuracy.
Namely, in general, within a disc drive or apparatus equipped with an optical pickup, there are mounted a laser diode which generates heat when it performs a recording/reproducing operation, a laser driver circuit board, a high frequency module, and plural numbers of parts or elements, such as a driver coil for use in an objective lens driver, etc., to be connected thermally, in a pickup housing made of metal, and heat generation of those heat-generating elements causes a local non-uniform temperature distribution within the pickup housing, thereby causing thermal interference between those heat-generating elements. In particular, with respect to multi-functions of the disc drive apparatus, various disc drive apparatuses have been developed which are equipped with a CD-R/RW function for recording information on the disc, a DVD-R/RW function for a disc of much larger recording capacity, and/or a DVD-RAM function, etc. In those disc drive apparatuses, the detection light (i.e., a laser light beam) emitted from the laser diode provided within the optical pickup typically has a very large output, and also a large number of heat-generating elements must be disposed in close proximity with each other, due to a demand for reduction in the size thereof. Because of those heat-generating elements, the following problems are created                (1) Thermal interference due to the close disposition of the heat-generating elements;        (2) Thermal deformation due to a locally non-uniform temperature distribution;        (3) A deterioration of the lifetime of elements due to heat; and        (4) A local rise in temperature inside of the apparatus due to heat radiation from the elements functioning as a heat source, and erroneous operation or malfunction in a circuit system.        